An acrylonitrile-butadiene-styrene copolymer (hereinafter, referred to as an “ABS resin”) thermoplastic resin is a material widely used in office appliances, electronic/electrical components, automobile interior materials and the like, due to its superior physical properties such as impact resistance, chemical resistance and processability. Methods for preparing such a resin are disclosed in U.S. Pat. Nos. 3,928,494, 4,520,165, 5,955,540, and 5,910,538 and European Patent Publication No. 0288298A and the like. These patents suggest techniques to improve physical properties such as impact strength, processability and gloss, but do not teach a technique associated with a thermoplastic ABS resin that exhibits excellent gloss as well as superior whiteness.
ABS resins are predominantly prepared by emulsion polymerization and are sometimes prepared by bulk polymerization. In accordance with the emulsion polymerization, a diene rubber latex is initially prepared by emulsion polymerization to impart impact strength, aromatic vinyl compound monomers and vinyl cyanide compound monomers are grafted to the rubber latex to prepare an acrylonitrile-butadiene-styrene copolymer, and the graft copolymer is then mixed with a styrene-acrylonitrile (hereinafter, referred to as a “SAN”) copolymer prepared by bulk polymerization to prepare a final ABS resin. The ABS resin prepared by this method exhibits superior impact resistance, processability and chemical resistance, but disadvantageously has a limitation of physical properties such as whiteness and thermal stability as well as of some loss due to the use of emulsifiers and coagulants. Meanwhile, the ABS resin prepared by bulk polymerization contains no emulsifier and thus exhibits superior whiteness and thermal stability. However, the ABS resin disadvantageously has a limitation of gloss due to use of large-diameter rubbers, and of physical properties such as impact resistance since it cannot contain rubbers in a predetermined amount or higher due to viscosity thereof.